A two-dimensional map of the color excess in NGC 3603.
PANG X., PASQUALI A. and GREBEL E.K.
Abstract (from CDS):
Using archival Hubble Space Telescope/Wide Field Camera 3 images centered on the young HD 97950 star cluster in the giant H II region NGC 3603, we computed the pixel-to-pixel distribution of the color excess, E(B - V)g, of the gas associated with this cluster from its Hα/Paβ flux ratio. At the assumed distance of 6.9 kpc, the resulting median color excess within 1 pc from the cluster center is E(B - V)g= 1.51±0.04 mag. Outside the cluster (at r > 1 pc), the color excess is seen to increase with cluster-centric distance toward both north and south, reaching a value of about 2.2 mag at r = 2 pc from the cluster center. The radial dependence of E(B - V)gwestward of the cluster appears rather flat at about 1.55 mag over the distance range 1.2 pc <r < 3 pc. In the eastern direction, E(B - V)g steadily increases from 1.5 mag at r = 1 pc to 1.7 mag at r = 2 pc and stays nearly constant at 1.7 mag for 2 pc <r < 3 pc. The different radial profiles and the pixel-to-pixel variations of E(B - V)g clearly indicate the presence of significant differential reddening across the 4.9 pcx4.3 pc area centered on the HD 97950 star cluster. We interpret the variations of E(B - V)g as the result of stellar radiation and stellar winds interacting with an inhomogeneous dusty local interstellar medium whose density varies spatially. From the E(B - V)g values measured along the rims of the prominent pillars MM1 and MM2 in the southwest and southeast of the HD 97950 cluster, we estimate an H2 column density of and extrapolate it to in the pillars' interior. We find the pillars to be closer to us than the central ionizing cluster and suggest that star formation may be occurring in the pillar heads.
dust, extinction - H II regions - open clusters and associations: individual: NGC 3603 - stars: massive - stars: winds, outflows